The present invention relates to a seat belt for protecting automobile passengers during collisions, and more particularly to an air belt having a bag-like portion, which is inflated by gas generated by a gas generator.
Japanese Unexamined Patent Publication No. 5-85301 describes a typical inflatable safety harness. FIG. 12(a) is a perspective view showing the inflatable air belt. FIG. 12(b) is a cross sectional view of the air belt shown in FIG. 12(a) taken along line B--B.
An air belt device 1 includes a shoulder belt 2, a lap belt 3, a buckle 4, a tongue 5, and an intermediate guide 6. The shoulder belt 2 extends diagonally from the right side of a passenger's body to the left side. The lap belt 3 extends across the passenger's body from the right to the left. The buckle 4 is secured to a floor, or the like of the vehicle body. The intermediate guide guides the shoulder belt 2.
The shoulder belt 2 has an ordinary belt 2a similar to the conventional seat belts, and a bag-like belt portion 2b attached to one end of the belt 2a. The intermediate guide 6 slidably supports the belt 2a. The other end of the belt 2a is connected to an emergency locking retractor (ELR), which is secured to the automobile body. The ELR winds and retracts the belt 2a.
The bag-like belt portion 2b engages with the passenger's body when in use. It has the tongue 5 at its free end opposite to the end that leads to the belt 2a.
The lap belt 3 is an ordinary and commonly available belt. One end of the lap belt 3 is connected to the tongue 5 while the other end of the belt is connected to the ELR, which is secured to the automobile body. The buckle 4 has a gas generator 9 to generate a high pressure gas upon accidents such as collisions.
A passage extends through the tongue 5 and the buckle 4 to allow flow of gas from the generator 9.
As shown in FIG. 12b, the bag-like portion 2b of the shoulder belt 2 includes a folded belt body 2c, as indicated by solid lines, and is enclosed in a cover 2d, the two edges of which are sewed to each other to form stitches 2e. Accordingly, the structure of the bag-like portion has a strap-like shape. Upon activation of the gas generator 9, the stitch 2e tears as the shoulder belt 2 inflates, and the bag-like portion 2b expands as shown by the double dotted line.
Employing a retractable webbing, which is attached to one end of the shoulder belt and is wound by a retractor, the air belt device described in Japanese Unexamined Publication No. 5-85301 ensures a large degree of freedom with respect to the passenger's upper body movement, where the webbing extends and retracts in response to the movements of the passenger. It would be required, however, that the winding force of the retractor 7 in the air belt in Japanese Unexamined Publication No. 5-85301 not be too strong to prevent the belt from pressing the passenger with excessive force. Due to the limitation on the winding force, the gap arises between the shoulder belt 2 and the passenger's body, requiring further expansion of the bag-like portion 2B upon a collision.